GENERAL BIOLOGY membrane and intercellular junctions Flashcards
Explain what endocytosis is.
It is the uptake of macromolecules by the formation of vesicle with the plasma membrane.
What are the three types of endocytosis?
Phagocytosis, pinocytosis and receptor mediated endocytosis.
State some differences between phagocytosis and pinocytosis?
Phagocytosis is specific, it surrounds stuff from outside the cell with cell membrane and creates food vacuole. Pinocytosis is unspecific, it is the uptake of extracellular fluid and solutes in that fluid.
Which junction mechanically hold cells together?
Anchoring junctions, in between animal cells.
Describe the structure of an anchoring junction?
It is made of plaques on the inner surface of cell membrane. Intermediate filaments reinforces the plaques and transmembrane proteins connect the plaque from adjacent cells. Keratin filaments reinforce desmosome in intercellular space.
What is the difference between desmosome and hemidesomosome ?
a desmosome is a junction between two cells and a hemidesmosome is a junction between a cell and connective tissue, also called an adherent junction.
Describe tight junctions.
Tight junctions are rows of tightly packed proteins that bind cells together. Their structure differs by cell type. The number and pattern of strands differ.
What are the functions of tight junctions?
They prevent the leakage of extracellular fluid. They also establish the polarity of cell membrane by preventing the membrane proteins from diffusing throughout the membrane.
Give three examples of tight junctions.
Intestinal epithelial cells, blood testes barrier and prevent water loss between skin cell. The blood testes barrier tight junctions prevent the white blood cell from the blood from attacking the haploid spermatozoa.
What happens when E. coli or salmonella disrupts tight junction?
There is excessive fluid loss.
Describe a gap junction.
A gap junction is a tunnel connecting the cytoplasms of two adjacent cells. It is a pore lined with a protein and it can open and close.
What is the function of a gap junction?
It allows the passage between cells of ions and small molecules.
What is the intercellular junction of plants cells?
It is called a plasmodesmata. It is a channel through the cell wall of adjacent cells. The plasma membrane between adjacent cell is continuous. It serves for the lateral transport of water and solutes.
